1. Field of the Disclosure
This disclosure relates to a backlight unit capable of implementing slimness and preventing a stain defect.
2. Description of the Related Art
It is the trend that liquid crystal display (LCD) devices are widening their application fields because of their features, such as their light weight, slimness, a low driving voltage, and so on. This trend is evidently confirmed in the ways in which the LCD devices have been applied to office automation equipment, audio equipment, video equipment, and so on. The LCD device controls a transmitting amount of light on the basis of image signals applied to a plurality of control switches, in order to display a picture.
The LCD device, which is not self-luminescent, includes a backlight unit irradiating light on the rear surface of an LCD panel in which a picture is displayed. The backlight unit is classified as either an edge type or a direct type in accordance with the disposition of its light source.
The edge type backlight unit includes a light source which is disposed in a position corresponding to a side of the LCD panel. Also, the edge type backlight unit irradiates light emitted from the light source on the entire surface of the LCD panel using a light guide panel. On the other hand, the direct type backlight unit includes a plurality of light sources arranged opposite the rear surface of the LCD panel. These plural light sources directly apply light to the rear surface of the LCD panel. The direct type backlight unit has a higher brightness and a wider luminescent surface than that of the edge type backlight unit because it employs plural light sources. In addition, the backlight unit becomes larger in size corresponding to the increased size of the LCD device. In view of these points, direct type backlight units are widely used in LCD devices.
Such a direct type backlight unit generates a brightness difference between regions which include a light source and those which do not. This results from the configuration in which plural light sources are arranged at fixed intervals on the rear surface of the LCD panel. To rectify this, a direct type backlight unit of the related art included in an LCD device increases the distance (or gap) between the light sources and a diffusion plate disposed above the light sources. Accordingly, the direct type backlight unit of the related art can prevent the brightness difference between regions which include a light source and those which do not. In other words, the direct type backlight unit of the related art can realize uniform brightness.
However, the direct type backlight unit used in a large-sized LCD device must maintain a sufficient distance (or gap) between the light sources and the diffusion plate in order to realize uniform brightness. Therefore, the direct type backlight unit of the related art makes it difficult to develop an LCD device of a size thin enough to meet the desires of customers.
Furthermore, light emission diodes (LED) recently used in backlight units as a light source greatly intensify the brightness difference between the regions in which they are disposed and those in which they are not. Due to this, stain defects are generated on an image displayed by the LCD device which employs the direct type backlight unit with LEDs.